Heart failure is a clinical problem of increasing importance. Heart failure is best considered a syndrome that results from any number of cardiac conditions in which the cardiovascular system is unable to meet the demands placed upon it.
Others have disclosed a pacemaker that responds to abnormal conditions of a patient's heart by delivering pacing therapy comprising electrical stimulation to the heart and electrical stimulation to nerves or ganglia in the autonomic nervous system.
Others have also disclosed an implantable medical device that prevents arrhythmia by detecting a risk for arrhythmia and stimulating afferent nerves to prevent the arrhythmia. The device monitors sympathetic and parasympathetic nerve activity for the assessment of arrhythmia risk.
Other have disclosed an implantable medical device for detecting imminent cardiac arrhythmia in response to nerve signal activity in the efferent autonomic nerve system, such that activity sensing circuitry emit an output implying arrhythmia based on sensed neural activity.
Others have also disclosed an external method and apparatus for measuring activity of the autonomic nerve system using ECG signals obtained from a patient at rest to quantify a degree of heart failure. The ECG signals are analyzed by measuring the R—R intervals, generating a Poincaré plot using the intervals, and analyzing the plots to determine a level of heart failure.
Others have also disclosed a method of constructing a unique statistical characteristic of a time series data of a measurable activity (such as the autonomic nerve system for diagnosing autonomic neuropathies). The method computes a Hurst exponent for the time series as a unique statistical characteristic.
There are continuing needs for methods and apparatus that can provide early detection of heart failure, for example, in patients with impaired cardiac systolic performance prior to the clinical recognition of such progressing failure.